GottaBeAStudent: Myth of Battery Life

Andrew Ferguson is an author at StudentTabletPC.com…when homework and exams permit. This is the first in a series of guest posts for GottaBeMobile.

This article was originally going to be about batteries and battery management. Well, it still is. But not in the way you might think. I wanted to write an awesome article about how I changed a few settings and all of a sudden I went from an hour of battery life to five hours of battery life.

This will not be that article.

I have a confession to make. Most of the time when my tablet is on, it’s plugged into the wall. At home, I drop it in my port replicator and it basically becomes a glorified desktop. I have a separate power cable in the living room that I plug into when I do homework. Another brick remains in my bag for when I’m out and about and I’m pretty sure I have a fourth one floating around somewhere “just in case.”

In short, my life revolves around power cables and where the electrical outlets are. This is somehow fitting considering that I’m at college to become an electrical engineer.

It seems to me that a lot of emphasis is placed on trying to get ÃƒÂ¼ber long battery times. I’ll often hear users wanting to buy a computer with a battery that will last them all day without having to plug in. This is not an entirely unreasonable request and with a battery big enough and a device that consumes a small enough amount of power, it can readily be accomplished.

I’m not going to bore you with the technical details about my power consumption. Instead, I’ll provide a brief overview of how I run my ship:

I usually keep my monitor brightness at 3/8 to 1/2 brightness.

There are three programs I almost always have running: OneNote, Mathematica, and Firefox. There are also a slew of programs running in my tray, such as Skype, Pidgin, AVG Antivirus, Mozy, Google Desktop, etc. My base RAM usage is around 900MB. I honestly have no idea how it got that high and I’m sure there is some memory leak somewhere, but I haven’t found it yet.

The lectures go pretty fast, so I need demand the maximum performance/speed from my machine so that I can switch between programs without issue and not miss a beat.

Running in the “Normal” power saving mode with the brightness cranked up one notch fits the bill pretty well. But as I alluded to earlier, it also takes its toll on my battery.

Most days, I get just over an hour of performance from my battery. All my classes are 50 minutes in length, so I can easily go a class period on a charge. However, the next class I’d have to plug in. On the first day of class, I make it my personal mission to find all the plugs in the classroom. From there, I can decided where to sit. I usually get pretty lucky and can find a plug in the front 1/3 of the classroom. Thus, my typical day ends up looking something like this:

9am – Fluid Mechanics – Battery

10am – Digital Logic – Wall

11am – Advanced Eng. Math – Battery

12pm – Lunch – Battery/Wall

2pm – Information Systems – Battery/Wall

3pm – Eng. Circuit Analysis – Wall

If I’m near a socket, I’ll usually plug in, even if I don’t need it. Might as well keep the tanked topped off.

A couple things I should note. First, I’ve going on four years with this computer and over two years with this battery. My tablet has regularly gets a good workout as I take it with my pretty much wherever I go. The point being that my battery has gone through and continues to go through many cycles.

A quick sidebar if I may: Most portable devices use Lithium Ion (Li-Ion) batteries. Li-Ion batteries have a fantastic energy density (around 600000 Joules/kg), over twice that of NiCad and NiMH batteries [1]. Practically no memory effect and a slow loss of charge [2] have made the technology the de facto solution for devices that need portability.

However, for all its greatness, Lithium Ion batteries are ancient by today’s technical standards, having been around for over 15 years [2]. While small leaps and bounds have been made in battery design, most of the advances come from better power management. Inevitably, even with perfect power management, greater computing capacity will require more power. To have more power available within the confines of the same device will require a battery with greater power density. Thus, in my opinion, the future of better battery life is not better management, but better technology.